How your credit card number checks itself (Luhn Algorithm)

The Luhn algorithm is the hidden piece of math from 1954 that catches your typos every time a checkout page flags an "invalid card number." What do your 16 credit card digits actually mean? Why is the last one a computed check digit? And how does the four-step mod 10 algorithm validate the rest? It's also the story of Hans Peter Luhn, the IBM engineer who pioneered the hash function, coined "business intelligence," and patented a cocktail machine. Why did Visa, Mastercard and American Express adopt the Luhn algorithm? How does it run on IMEI numbers, SIM cards and even McDonald's receipts? And why did the superior Verhoeff and Damm algorithms lose? All of this is the story of the Luhn algorithm. What's inside: 00:00 — Intro 00:57 — Chapter 1: Card Number Mystery 02:01 — Chapter 2: Luhn's Algorithm 07:47 — Chapter 3: Genius Inventor 10:50 — Chapter 4: Conquering the World 15:16 — Chapter 5: Three Takeaways